1. Field of the Invention
The present invention relates to an apparatus for generating musical tones and, particularly, to an apparatus for generating tone signals using impulse response signals.
2. Description of the Background
In the conventional apparatus for forming musical tones, the impulse response waveform signals have not been controlled. The impulse response waveform signals are simply sampled and stored, and are repetitively read out, the period of repetition varying depending upon a specified pitch. In this case, the period of repetition becomes shorter with an increase in the specified pitch, and the period of repetition becomes longer with a decrease in the specified pitch. The rate of reading out the impulse response waveform signals remains constant and does not change irrespective of whether the pitch is high or low.
According to the conventional apparatus, however, the impulse response waveform signals could be simply read out and applied to musical tones, but the timbre of the musical tone could not be varied. The frequency components (characteristics) of musical tone vary depending upon the filters, and the timbre of musical tone can be changed.
However, the frequency characteristics (spectral envelope) of musical tone vary depending upon a change in the rate of reading the impulse response waveform signals (depending upon the rate of generation of the impulse response waveform signals). As the rate of generating the impulse response wave signals changes, the frequency characteristics expand or contract on a frequency axis, whereby the frequency characteristics vary and the timbre changes. In this case, when the rate of reading the impulse response waveform signals is interlocked to the recurring period of reading, the timbre is not determined independently of the pitch; i.e., the timbre varies depending upon the pitch.